Transcript Slide 1

Summaries – 1
BI-311
The Historical Roots of Microbiology: The Science
Ferdinand Cohn
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Founded the field of bacteriology
Recognized distinction between
prokaryotic and eukaryotic
cellular organization
Discovered bacterial endospores
The Historical Roots of Microbiology:
Louis Pasteur
• Discredited the theory of Spontaneous
Generation.
• Introduced control of microbial growth.
• Discovered lactic acid bacteria
• Role of yeast in alcohol fermentation
• Rabies vaccine
The Historical Roots of Microbiology:
Robert Koch
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Growth of pure cultures of microorganisms
Solid growth media
Discovered cause of tuberculosis.
Developed criteria for the study of infectious
microorganisms
• Kochst Postulates.
Koch’s Postulates
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OBSERVE: The presence of suspected
pathogenic microorganism correlates positively
with the symptoms of the diseased and negative
with healthy control
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ISOLATE the suspected pathogen into axenic
culture
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INFECT a healthy animal with cultured strain.
Observe whether the same symptoms show
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RE-ISOLATE the pathogen from the new
victim and compare both cultures
The Historical Roots of Microbiology: General Microbiology
- Microbial Ecology and Diversity
Martinus Beijerinck
• Enrichment Culture Technique
• Concept of Virus
Sergey Winogradsky
• Concept of Chemolithotrophy and
Autotrophy
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fungi
EUKARYOTES
“Crown species”
Protoctista
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Monera
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Five Kingdoms
PROKARYOTES
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Incident light microscopy (dissecting)
Transmitted light microscopy (compound)
Phase contrast
Dark field
Differential Interference Contrast (DIC)
Fluorescence microscopy
Confocal Scanning Light Microcopy (CSLM),
Transmission electron microscopy (TEM)
Scanning electron microscopy (SEM)
The atomic force microscope
• Differential Interference Contrast (DIC) and
Confocal Scanning Light Microcopy (CSLM)
allow for greater three-dimensional imaging
than other forms of light microscopy,
• Confocal microscopy allows imaging through
thick specimens.
• The atomic force microscope yields a
detailed three-dimensional image of live
preparations.
Electron microscopes
use electron beams instead of light. They have
far greater resolving power than do light
microscopes, the limits of resolution being about
0.2 nm. Two major types of electron microscopy
are performed:
Transmission Electron Microscopy (TEM), for
observing internal cell structure down to the
molecular level, and
Scanning Electron Microscopy (SEM), useful for
three-dimensional imaging and for examining
surfaces.
Scanning Electron Microscopy – SEM
Glutaraldehyde-fixed, critical point-dried, goldpaladium coated
Eukaryotic cell
Freeze-etched preparation
Carbon-coated,
Gold-shaded, TEM image
Macromolecule
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• Organic chemistry = chemistry of carbon
• Biochemistry = chemistry of macromolecules
• Water = solvent & chemical bonding
properties: polarity, hidrophilic vs. hydrophobic
H-bonds, glycosidic, esteric, etheric, peptide.
• Biogenic elements = C, O, H, N, S, P construct
polymers from monomers: polysaccharides,
(phospho-)lipids, polypeptides, polynucleotides
CARBOXYL
ESTER
ETHER
ALDEHYDE
ALCOHOL
PHOSPHO-ESTER
ACID ANHYDRIDE
KETO
THIOESTER
PHOSPHO ANHYDRIDE
• The cell walls of Bacteria contain a polysaccharide
called peptidoglycan.
• This material consists of strands of alternating
repeats of N-acetylglucosamine and Nacetylmuramic acid, with the latter cross-linked
between strands by short peptides. Many sheets of
peptidoglycan can be present, depending on the
organism.
• Archaea lack peptidoglycan but contain walls made
of other polysaccharides or of protein. The enzyme
lysozyme destroys peptidoglycan, leading to cell lysis
in Bacteria but not in Archaea
• In addition to peptidoglycan, gram-negative
Bacteria contain an outer membrane
consisting of lipopolysaccharide, protein, and
lipoprotein.
• Proteins called porins allow for permeability
across the outer membrane.
•The space between the membranes is the
periplasm, which contains various proteins
involved in important cellular functions.
Prokaryotic cells often contain various surface
structures. These include:
fimbriae
pili
S-layers
capsules
slime layers.
These structures have several functions,
but a key one is in attaching cells to a solid
surface.
Prokaryotic cells often contain internal
granules such as sulfur, PHB, polyphosphate,
PHAs, and magnetosomes. These substances
function as storage materials or in
magnetotaxis.
Gas vesicles are small gas-filled structures
made of protein that function to confer
buoyancy on cells. Gas vesicles contain two
different proteins arranged to form a gas
permeable, but watertight structure: Gas
Vesicle Proteins GVP-a and GVP-c.
The endospore is a highly resistant
differentiated bacterial cell produced by
certain gram-positive Bacteria.
• Endospore formation leads to a highly
dehydrated structure that contains essential
macromolecules and a variety of substances
such as calcium dipicolinate and small acidsoluble proteins, absent from vegetative cells.
• Endospores can remain dormant indefinitely
but germinate quickly when the appropriate
trigger is applied.
• Motility in most microorganisms is due to
flagella. In prokaryotes the flagellum is a
complex structure made of several proteins.
• Most of these proteins are anchored in the
cell wall and cytoplasmic membrane.
• The flagellum filament, which is made of a
single kind of protein, rotates at the expense
of the proton motive force, which drives the
flagellar motor.
Prokaryotes that move by gliding motility do
not employ rotating flagella, but instead creep
along a solid surface by any of several
possible mechanisms.
Motile bacteria can respond to chemical and
physical gradients in their environment.
• In the processes of chemotaxis and
phototaxis, random movement of a prokaryotic
cell can be biased either toward or away from
a stimulus by controlling the degree to which
runs or tumbles occur.
• The latter are controlled by the direction of
rotation of the flagellum, which in turn is
controlled by a network of sensory and
response proteins.
Microbial Metabolism
• Biocatalysis & Energy Generation
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Phosphorylation
Oxidation & Reduction
Fermentation & Respiration
Chemiosmosis: Proton Motive Force
ATPase Motor
Energy Yielding Metabolic Systems
Biosynthesis
∆G0' versus ∆G
standard conditions pH 7, 25°C
• The chemical reactions of the cell are
accompanied by changes in energy,
measured in kilojoules (kJ).
• A chemical reaction can occur with the
release of free energy (exergonic) or with
the consumption of free energy
(endergonic).
• 1 calorie = 4.186 Joules
Energy
G 0’f = free Energy of formation
for elements G 0’f = 0
ΔG 0’ = change in free Energy in reactions
ΔG 0’ of the reaction: A+B  C+D equals
ΔG 0’ [C+D] - ΔG 0’ [A+B]
products - reactants
if + , the reaction is ENDERGONIC
if - , the reaction is EXERGONIC
ΔG 0’ does not affect the rates of reaction
• The reactants in a chemical reaction must
first be activated before the reaction can
take place, and this requires a catalyst.
• Enzymes are catalytic proteins that speed
up the rate of biochemical reactions.
• Enzymes are highly specific in the
reactions they catalyze, and this
specificity resides in the threedimensional structure of the
polypeptide(s) in the protein.
Enzyme Biocatalysis
• Specific substrate binding
• Substrate orientation o active sites
• Lowering the activation energy
• The energy released in redox reactions is
conserved in the formation of certain
compounds that contain energy-rich
phosphate or sulfur bonds. The most
common of these compounds is ATP, the
prime energy carrier in the cell.
• Long-term storage of energy is linked to
the formation of polymers, which can be
consumed to yield ATP.
Microbial Metabolism
• Biocatalysis & Energy Generation
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Phosphorylation
Oxidation & Reduction
Fermentation & Respiration
Chemiosmosis: Proton Motive Force
ATPase Motor
Energy Yielding Metabolic Systems
Biosynthesis
Oxidation–reduction reactions
involve the transfer of electrons from
electron donor to electron acceptor.
The tendency of a compound to
accept or release electrons is
expressed quantitatively by its
reduction potential, E0’.
• The transfer of electrons from donor
to acceptor in a cell typically
involves one or more electron
carriers.
• Some electron carriers are
membrane-bound, whereas others,
such as NAD+/NADH, are freely
diffusible, transferring electrons from
one place to another in the cell.
The energy released in redox reactions
is conserved in the formation of certain
compounds that contain energy-rich
phosphate or sulfur bonds.
• The most common of these compounds
is ATP, the prime energy carrier in the
cell.
• Long-term storage of energy is linked to
the formation of polymers, which can
be consumed to yield ATP.
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• Fermentation and respiration are the
two means by which chemoorganotrophs conserve energy from
the oxidation of organic compounds.
• During these catabolic reactions,
ATP synthesis occurs by way of
either substrate-level
phosphorylation (fermentation) or
oxidative phosphorylation
(respiration).
• Glycolysis is a major pathway of
fermentation and is a widespread
means of anaerobic metabolism.
• The end result of glycolysis is the
release of a small amount of energy
that is conserved as ATP and the
production of fermentation products.
• For each glucose consumed in
glycolysis, 2 ATPs are produced.
Respiration involves the complete
oxidation of an organic compound with
much greater energy release than
during fermentation. The citric acid
cycle plays a major role in the
respiration of organic compounds.
Respiration involves the complete
oxidation of an organic compound with
much greater energy release than
during fermentation. The citric acid
cycle plays a major role in the
respiration of organic compounds.
• When electrons are transported
through an electron transport chain,
protons are extruded to the outside
of the membrane forming the proton
motive force.
• Key electron carriers include flavins,
quinones, the cytochrome bc1
complex, and other cytochromes,
depending on the organism.
• The cell uses the proton motive force
to make ATP through the activity of
ATPase.
• Chemo –
Energy from chemical reactions
• Organo –
of organic compounds
• Hetero –
Carbon from organic sources
– trophic
feeding
• Electron acceptors other than O2 can
function as terminal electron acceptors
for energy generation. Because O2 is
absent under these conditions, the
process is called anaerobic respiration.
• Chemolithotrophs use inorganic
compounds as electron donors, while
phototrophs use light to form a proton
motive force.
• The proton motive force is involved in all
forms of respiration and photosynthesis.
Energy from:
Chemical reactions
or
Chemo-
Light
Photo-
of:
inorganic or organic
compounds
Litho-
Organo-
Source of carbon :
CO2
Auto-
or
(CH2O)n
Hetero-
Amino acids are formed from
carbon skeletons generated during
catabolism while nucleotides are
biosynthesized using carbon from
several sources.
Lipids
Fatty acids are synthesized two
carbons at a time and then attached to
glycerol to form lipids.